--[[
This file is part of Courseplay (https://github.com/Courseplay/Courseplay_FS22)
Copyright (C) 2021 Peter Vaiko

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.

Drive strategy for driving a field work course

]]--

---@class AIDriveStrategyFieldWorkCourse : AIDriveStrategyCourse
AIDriveStrategyFieldWorkCourse = {}
local AIDriveStrategyFieldWorkCourse_mt = Class(AIDriveStrategyFieldWorkCourse, AIDriveStrategyCourse)

AIDriveStrategyFieldWorkCourse.myStates = {
    WORKING = {},
    ON_CONNECTING_TRACK = {},
    WAITING_FOR_LOWER = {},
    WAITING_FOR_LOWER_DELAYED = {},
    WAITING_FOR_STOP = {},
    WAITING_FOR_WEATHER = {},
    TURNING = {},
    TEMPORARY = {},
}

AIDriveStrategyFieldWorkCourse.normalFillLevelFullPercentage = 99.5

function AIDriveStrategyFieldWorkCourse.new(customMt)
    if customMt == nil then
        customMt = AIDriveStrategyFieldWorkCourse_mt
    end
    local self = AIDriveStrategyCourse.new(customMt)
    AIDriveStrategyCourse.initStates(self, AIDriveStrategyFieldWorkCourse.myStates)
    self.state = self.states.INITIAL
    -- cache for the nodes created by TurnContext
    self.turnNodes = {}
    -- course offsets dynamically set by the AI and added to all tool and other offsets
    self.aiOffsetX, self.aiOffsetZ = 0, 0
    self.debugChannel = CpDebug.DBG_FIELDWORK
    return self
end

function AIDriveStrategyFieldWorkCourse:delete()
    AIDriveStrategyFieldWorkCourse:superClass().delete(self)
    self:raiseImplements()
    TurnContext.deleteNodes(self.turnNodes)
    self:rememberWaypointToContinueFieldWork()
end

--- Start a fieldwork course. We expect that something else dropped us off close enough to startIx so
--- the most we need is an alignment course to lower the implements
function AIDriveStrategyFieldWorkCourse:start(course, startIx, jobParameters)
    self:showAllInfo('Starting field work at waypoint %d', startIx)
    self:updateFieldworkOffset(course)
    self.fieldWorkCourse = course
    -- remember at which waypoint we started, especially for the convoy
    self.startWaypointIx = startIx
    self.vehiclesInConvoy = {}

    local distance = course:getDistanceBetweenVehicleAndWaypoint(self.vehicle, startIx)

    ---@type CpAIJobFieldWork
    local job = self.vehicle:getJob()
    local alignmentCourse, alignmentCourseStartIx = job:getStartFieldWorkCourse()

    if alignmentCourse then
        -- there is an alignment course already created by the AIDriveStrategyDriveToFieldWorkStart,
        -- and we are supposed to continue on that one
        self:debug('Continuing the alignment course at %d to start work.', alignmentCourseStartIx)
        -- make sure the alignment course is used only once
        job:setStartFieldWorkCourse(nil, nil)
        self.course = course
        self:startAlignmentTurn(course, startIx, alignmentCourse, alignmentCourseStartIx)
    elseif distance > 2 * self.turningRadius then
        self:debug('Start waypoint is far (%.1f m), use alignment course to get there.', distance)
        self.course = course
        self:startAlignmentTurn(course, startIx)
    else
        self:debug('Close enough to start waypoint %d, no alignment course needed', startIx)
        self:startCourse(course, startIx)
        self.state = self.states.INITIAL
    end
end

function AIDriveStrategyFieldWorkCourse:update(dt)
    AIDriveStrategyFieldWorkCourse:superClass().update(self)
    if CpDebug:isChannelActive(CpDebug.DBG_TURN, self.vehicle) then
        if self.state == self.states.TURNING or self.state == self.states.DRIVING_TO_WORK_START_WAYPOINT then
            if self.turnContext then
                self.turnContext:drawDebug()
            end
            if self.aiTurn then
                self.aiTurn:drawDebug()
            end
        end
        -- TODO_22 check user setting
        if self.course:isTemporary() then
           self.course:draw()
        elseif self.ppc:getCourse():isTemporary() then
            self.ppc:getCourse():draw()
        end
    end
    if CpDebug:isChannelActive(CpDebug.DBG_PATHFINDER, self.vehicle) then
        if self.pathfinder then
            PathfinderUtil.showNodes(self.pathfinder)
        end
    end
    if self.fieldWorkerProximityController then
        self.fieldWorkerProximityController:draw()
    end
    self:updateImplementControllers(dt)
end

--- This is the interface to the Giant's AIFieldWorker specialization, telling it the direction and speed
function AIDriveStrategyFieldWorkCourse:getDriveData(dt, vX, vY, vZ)

    self:updateFieldworkOffset(self.course)
    self:updateLowFrequencyImplementControllers()

    local moveForwards = not self.ppc:isReversing()
    local gx, gz

    ----------------------------------------------------------------
    if not moveForwards then
        local maxSpeed
        gx, gz, maxSpeed = self:getReverseDriveData()
        self:setMaxSpeed(maxSpeed)
    else
        gx, _, gz = self.ppc:getGoalPointPosition()
    end
    ----------------------------------------------------------------
    if self.state == self.states.INITIAL then
        self:setMaxSpeed(0)
        self.state = self.states.WAITING_FOR_LOWER
        self:lowerImplements()
    elseif self.state == self.states.WAITING_FOR_LOWER then
        self:setMaxSpeed(0)
        if self.vehicle:getCanAIFieldWorkerContinueWork() then
            self:debug('all tools ready, start working')
            self.state = self.states.WORKING
        else
            self:debugSparse('waiting for all tools to lower')
        end
    elseif self.state == self.states.WAITING_FOR_LOWER_DELAYED then
        -- getCanAIVehicleContinueWork() seems to return false when the implement being lowered/raised (moving) but
        -- true otherwise. Due to some timing issues it may return true just after we started lowering it, so this
        -- here delays the check for another cycle.
        self.state = self.states.WAITING_FOR_LOWER
        self:setMaxSpeed(0)
    elseif self.state == self.states.WAITING_FOR_PATHFINDER then
        self:setMaxSpeed(0)
    elseif self.state == self.states.WORKING then
        self:setMaxSpeed(self.settings.fieldWorkSpeed:getValue())
    elseif self.state == self.states.TURNING or self.state == self.states.DRIVING_TO_WORK_START_WAYPOINT then
        -- we use a turn for driving to the waypoint to start working
        local turnGx, turnGz, turnMoveForwards, turnMaxSpeed = self.aiTurn:getDriveData(dt)
        self:setMaxSpeed(turnMaxSpeed)
        -- if turn tells us which way to go, use that, otherwise just do whatever PPC tells us
        gx, gz = turnGx or gx, turnGz or gz
        if turnMoveForwards ~= nil then moveForwards = turnMoveForwards end
    elseif self.state == self.states.ON_CONNECTING_TRACK then
        self:setMaxSpeed(self.settings.fieldSpeed:getValue())
    end

    self:setAITarget()
    self:limitSpeed()
    self:checkProximitySensors(moveForwards)
    self:checkDistanceToOtherFieldWorkers()

    return gx, gz, moveForwards, self.maxSpeed, 100
end

function AIDriveStrategyFieldWorkCourse:checkDistanceToOtherFieldWorkers()
    -- keep away from others working on the same course
    self:setMaxSpeed(self.fieldWorkerProximityController:getMaxSpeed(self.settings.convoyDistance:getValue(), self.maxSpeed))
end

-- Seems like the Giants AIDriveStrategyCollision needs these variables on the vehicle to be set
-- to calculate an accurate path prediction
function AIDriveStrategyFieldWorkCourse:setAITarget()
    --local dx, _, dz = localDirectionToWorld(self.vehicle:getAIDirectionNode(), 0, 0, 1)
    local wp = self.ppc:getCurrentWaypoint()
    --- TODO: For some reason wp.dx and wp.dz are nil sometimes.
    local dx, dz = wp.dx or 0, wp.dz or 0
    local length = MathUtil.vector2Length(dx, dz)
    dx = dx / length
    dz = dz / length
    self.vehicle.aiDriveDirection = { dx, dz }
    local x, _, z = getWorldTranslation(self.vehicle:getAIDirectionNode())
    self.vehicle.aiDriveTarget = { x, z }
end

-----------------------------------------------------------------------------------------------------------------------
--- Implement handling
-----------------------------------------------------------------------------------------------------------------------
function AIDriveStrategyFieldWorkCourse:initializeImplementControllers(vehicle)

    local defaultDisabledStates = {
        self.states.ON_CONNECTING_TRACK,
        self.states.TEMPORARY,
        self.states.TURNING,
        self.states.DRIVING_TO_WORK_START_WAYPOINT
    }
    self:addImplementController(vehicle, BalerController, Baler, {})
    self:addImplementController(vehicle, BaleWrapperController, BaleWrapper, defaultDisabledStates)
    self:addImplementController(vehicle, BaleLoaderController, BaleLoader, defaultDisabledStates)
    self:addImplementController(vehicle, APalletAutoLoaderController, nil, {}, "spec_aPalletAutoLoader")
    self:addImplementController(vehicle, UniversalAutoloadController, nil, {}, "spec_universalAutoload")

    self:addImplementController(vehicle, FertilizingSowingMachineController, FertilizingSowingMachine, defaultDisabledStates)
    self:addImplementController(vehicle, ForageWagonController, ForageWagon, defaultDisabledStates)
    self:addImplementController(vehicle, SowingMachineController, SowingMachine, defaultDisabledStates)
    self:addImplementController(vehicle, FertilizingCultivatorController, FertilizingCultivator, defaultDisabledStates)
    self:addImplementController(vehicle, MowerController, Mower, defaultDisabledStates)

    self:addImplementController(vehicle, RidgeMarkerController, RidgeMarker, defaultDisabledStates)

    self:addImplementController(vehicle, PickupController, Pickup, defaultDisabledStates)
    self:addImplementController(vehicle, SprayerController, Sprayer, {})
    self:addImplementController(vehicle, CutterController, Cutter, {}) --- Makes sure the cutter timer gets reset always.
    self:addImplementController(vehicle, StonePickerController, StonePicker, defaultDisabledStates)

    self:addImplementController(vehicle, MotorController, Motorized, {})
    self:addImplementController(vehicle, WearableController, Wearable, {})
    self:addImplementController(vehicle, VineCutterController, VineCutter, defaultDisabledStates)

    self:addImplementController(vehicle, SoilSamplerController, nil, defaultDisabledStates, "spec_soilSampler")

end

function AIDriveStrategyFieldWorkCourse:lowerImplements()    
    --- Lowers all implements, that are available for the giants field worker.
    for _, implement in pairs(self.vehicle:getAttachedAIImplements()) do
        implement.object:aiImplementStartLine()
    end
    self.vehicle:raiseStateChange(Vehicle.STATE_CHANGE_AI_START_LINE)

    if AIUtil.hasAIImplementWithSpecialization(self.vehicle, SowingMachine) or self.ppc:isReversing() then
        -- sowing machines want to stop while the implement is being lowered
        -- also, when reversing, we assume that we'll switch to forward, so stop while lowering, then start forward
        self.state = self.states.WAITING_FOR_LOWER_DELAYED
    end
    --- Lowers implements, that are not covered by giants.
    self:raiseControllerEvent(self.onLoweringEvent)
end

function AIDriveStrategyFieldWorkCourse:shouldRaiseImplements(turnStartNode)
    -- see if the vehicle has AI markers -> has work areas (built-in implements like a mower or cotton harvester)
    local doRaise = self:shouldRaiseThisImplement(self.vehicle, turnStartNode)
    -- and then check all implements
    for _, implement in pairs(AIUtil.getAllAIImplements(self.vehicle)) do
        -- only when _all_ implements can be raised will we raise them all, hence the 'and'
        doRaise = doRaise and self:shouldRaiseThisImplement(implement.object, turnStartNode)
    end
    return doRaise
end

---@param turnStartNode number at the last waypoint of the row, pointing in the direction of travel. This is where
--- the implement should be raised when beginning a turn
function AIDriveStrategyFieldWorkCourse:shouldRaiseThisImplement(object, turnStartNode)
    local aiFrontMarker, _, aiBackMarker = WorkWidthUtil.getAIMarkers(object, true)
    -- if something (like a combine) does not have an AI marker it should not prevent from raising other implements
    -- like the header, which does have markers), therefore, return true here
    if not aiBackMarker or not aiFrontMarker then return true end
    local marker = self:getImplementRaiseLate() and aiBackMarker or aiFrontMarker
    -- turn start node in the back marker node's coordinate system
    local _, _, dz = localToLocal(marker, turnStartNode, 0, 0, 0)
    self:debugSparse('%s: shouldRaiseImplements: dz = %.1f', CpUtil.getName(object), dz)
    -- marker is just in front of the turn start node
    return dz > 0
end


--- When finishing a turn, is it time to lower all implements here?
-- TODO: remove the reversing parameter and use ppc to find out once not called from turn.lua
function AIDriveStrategyFieldWorkCourse:shouldLowerImplements(turnEndNode, reversing)
    -- see if the vehicle has AI markers -> has work areas (built-in implements like a mower or cotton harvester)
    local doLower, vehicleHasMarkers, dz = self:shouldLowerThisImplement(self.vehicle, turnEndNode, reversing)
    if not vehicleHasMarkers and reversing then
        -- making sure the 'and' below will work if reversing and the vehicle has no markers
        doLower = true
    end
    -- and then check all implements
    for _, implement in ipairs(AIUtil.getAllAIImplements(self.vehicle)) do
        if reversing then
            -- when driving backward, all implements must reach the turn end node before lowering, hence the 'and'
            doLower = doLower and self:shouldLowerThisImplement(implement.object, turnEndNode, reversing)
        else
            -- when driving forward, if it is time to lower any implement, we'll lower all, hence the 'or'
            local lowerThis, _, thisDz = self:shouldLowerThisImplement(implement.object, turnEndNode, reversing)
            dz = dz and math.max(dz , thisDz) or thisDz
            doLower = doLower or lowerThis
        end
    end
    return doLower, dz
end

---@param object table is a vehicle or implement object with AI markers (marking the working area of the implement)
---@param turnEndNode number node at the first waypoint of the row, pointing in the direction of travel. This is where
--- the implement should be in the working position after a turn
---@param reversing boolean are we reversing? When reversing towards the turn end point, we must lower the implements
--- when we are _behind_ the turn end node (dz < 0), otherwise once we reach it (dz > 0)
---@return boolean, boolean, number the second one is true when the first is valid, and the distance to the work start
--- in meters (<0) when driving forward, nil when driving backwards.
function AIDriveStrategyFieldWorkCourse:shouldLowerThisImplement(object, turnEndNode, reversing)
    local aiLeftMarker, aiRightMarker, aiBackMarker = WorkWidthUtil.getAIMarkers(object, true)
    if not aiLeftMarker then return false, false, nil end
    local dxLeft, _, dzLeft = localToLocal(aiLeftMarker, turnEndNode, 0, 0, 0)
    local dxRight, _, dzRight = localToLocal(aiRightMarker, turnEndNode, 0, 0, 0)
    local dxBack, _, dzBack = localToLocal(aiBackMarker, turnEndNode, 0, 0, 0)
    local loweringDistance
    if AIUtil.hasAIImplementWithSpecialization(self.vehicle, SowingMachine) then
        -- sowing machines are stopped while lowering, but leave a little reserve to allow for stopping
        -- TODO: rather slow down while approaching the lowering point
        loweringDistance = 0.5
    else
        -- others can be lowered without stopping so need to start lowering before we get to the turn end to be
        -- in the working position by the time we get to the first waypoint of the next row
        loweringDistance = math.min(self.vehicle.lastSpeed, self.settings.turnSpeed:getValue() / 3600) *
                self.loweringDurationMs + 0.5 -- vehicle.lastSpeed is in meters per millisecond
    end
    local dzFront = (dzLeft + dzRight) / 2
    local dxFront = (dxLeft + dxRight) / 2
    self:debug('%s: dzLeft = %.1f, dzRight = %.1f, dzFront = %.1f, dxFront = %.1f, dzBack = %.1f, loweringDistance = %.1f, reversing %s',
            CpUtil.getName(object), dzLeft, dzRight, dzFront, dxFront, dzBack, loweringDistance, tostring(reversing))
    local dz = self:getImplementLowerEarly() and dzFront or dzBack
    if reversing then
        return dz < 0 , true, nil
    else
        -- dz will be negative as we are behind the target node. Also, dx must be close enough, otherwise
        -- we'll lower them way too early if approaching the turn end from the side at about 90° (and we
        -- want a constant value here, certainly not the loweringDistance which changes with the current speed
        -- and thus introduces a feedback loop, causing the return value to oscillate, that is, we say should be
        -- lowered, than the vehicle stops, but now the loweringDistance will be low, so we say should not be
        -- lowering, vehicle starts again, and so on ...
        local normalLoweringDistance = self.loweringDurationMs * self.settings.turnSpeed:getValue() / 3600
        return dz > - loweringDistance and math.abs(dxFront) < normalLoweringDistance * 1.5, true, dz
    end
end

--- Are all implements now aligned with the node? Can be used to find out if we are for instance aligned with the
--- turn end node direction in a question mark turn and can start reversing.
function AIDriveStrategyFieldWorkCourse:areAllImplementsAligned(node)
    -- see if the vehicle has AI markers -> has work areas (built-in implements like a mower or cotton harvester)
    local allAligned = self:isThisImplementAligned(self.vehicle, node)
    -- and then check all implements
    for _, implement in ipairs(AIUtil.getAllAIImplements(self.vehicle)) do
        -- _all_ implements must be aligned, hence the 'and'
        allAligned = allAligned and self:isThisImplementAligned(implement.object, node)
    end
    return allAligned
end

function AIDriveStrategyFieldWorkCourse:isThisImplementAligned(object, node)
    local aiFrontMarker, _, _ = WorkWidthUtil.getAIMarkers(object, true)
    if not aiFrontMarker then return true end
    return CpMathUtil.isSameDirection(aiFrontMarker, node, 2)
end

-----------------------------------------------------------------------------------------------------------------------
--- Event listeners
-----------------------------------------------------------------------------------------------------------------------
function AIDriveStrategyFieldWorkCourse:onWaypointChange(ix, course)
    if self.state ~= self.states.TURNING and self.state ~= self.states.DRIVING_TO_WORK_START_WAYPOINT
            and self.state ~= self.states.ON_CONNECTING_TRACK
            and self.course:isTurnStartAtIx(ix) then
        if self.state == self.states.INITIAL then
            self:debug('Waypoint change (%d) to turn start right after starting work, lowering implements.', ix)
            self:lowerImplements()
            -- otherwise we'd skip the wait for lowering states.
        end
        self:startTurn(ix)
    elseif self.state == self.states.ON_CONNECTING_TRACK then
        if not self.course:isOnConnectingTrack(ix) then
            -- reached the end of the connecting track, back to work
            self:debug('connecting track ended, back to work, first lowering implements.')
            self.state = self.states.WORKING
            self:lowerImplements()
        elseif self.course:isTurnStartAtIx(ix) and
                not self.course:isOnConnectingTrack(ix + 1) and
                not self.course:isOnHeadland(ix + 1)then
            self:debug('ending connecting track with a turn into the up/down rows')
            self:startTurn(ix)
        end
    elseif self.state == self.states.WORKING then
        -- towards the end of the field course make sure the implement reaches the last waypoint
        -- TODO: this needs refactoring, for now don't do this for temporary courses like a turn as it messes up reversing
        if ix > self.course:getNumberOfWaypoints() - 3 and not self.course:isTemporary() then
            local _, bm = self:getFrontAndBackMarkers()
            self:debug('adding offset (%.1f front marker) to make sure we do not miss anything when the course ends', bm)
            self.aiOffsetZ = -bm
        end
    end
end

function AIDriveStrategyFieldWorkCourse:onWaypointPassed(ix, course)
    if self.state == self.states.WORKING then
        -- check for transition to connecting track, make sure we've been on it for a few waypoints already
        -- to avoid raising the implements too soon, this can be a problem with long implements not yet reached
        -- the end of the headland track while the tractor is already on the connecting track
        if self.course:isOnConnectingTrack(self.course:getCurrentWaypointIx()) and self.course:isOnConnectingTrack(ix) and self.course:isOnConnectingTrack(ix - 2) then
            -- reached a connecting track (done with the headland, move to the up/down row or vice versa),
            -- raise all implements while moving
            self:debug('on a connecting track now, raising implements.')
            self:raiseImplements()
            self.state = self.states.ON_CONNECTING_TRACK
        end
            self:checkTransitionFromConnectingTrack(ix, course)
    elseif self.state == self.states.ON_CONNECTING_TRACK then
        self:checkTransitionFromConnectingTrack(ix, course)
    end
    if course:isLastWaypointIx(ix) then
        self:onLastWaypointPassed()
    end
end

--- Called when the last waypoint of a course is passed
function AIDriveStrategyFieldWorkCourse:onLastWaypointPassed()
    -- reset offset we used for the course ending to not miss anything
    self.aiOffsetZ = 0
    self:debug('Last waypoint of the course reached.')
    -- by default, stop the job
    self:finishFieldWork()
end

-----------------------------------------------------------------------------------------------------------------------
--- Turn
-----------------------------------------------------------------------------------------------------------------------
function AIDriveStrategyFieldWorkCourse:startTurn(ix)
    self:debug('Starting a turn at waypoint %d', ix)
    local fm, bm = self:getFrontAndBackMarkers()
    self.ppc:setShortLookaheadDistance()
    self.turnContext = TurnContext(self.vehicle, self.course, ix, ix + 1, self.turnNodes, self:getWorkWidth(), fm, bm,
            self:getTurnEndSideOffset(), self:getTurnEndForwardOffset())
    if AITurn.canMakeKTurn(self.vehicle, self.turnContext, self.workWidth, self:isTurnOnFieldActive()) then
        self.aiTurn = KTurn(self.vehicle, self, self.ppc, self.turnContext, self.workWidth)
    else
        self.aiTurn = CourseTurn(self.vehicle, self, self.ppc, self.turnContext, self.course, self.workWidth)
    end
    self.state = self.states.TURNING
end

function AIDriveStrategyFieldWorkCourse:isTurning()
    return self.state == self.states.TURNING    
end

-----------------------------------------------------------------------------------------------------------------------
--- State changes
-----------------------------------------------------------------------------------------------------------------------
function AIDriveStrategyFieldWorkCourse:finishFieldWork()
    self:debug('Course ended, stopping job.')
    self.vehicle:stopCurrentAIJob(AIMessageSuccessFinishedJob.new())
end

function AIDriveStrategyFieldWorkCourse:changeToFieldWork()
    self:debug('change to fieldwork')
    self.state = self.states.WAITING_FOR_LOWER_DELAYED
    self:lowerImplements(self.vehicle)
end

--- Start alignment turn, that is, a course to the waypoint of fieldWorkCourse where the
--- fieldwork should begin. This is performed as a turn maneuver, more specifically the end of the
--- turn maneuver where the work is started and has the logic to lower the implements exactly
--- where it needs to be.
---
--- (It is called alignment because it makes sure the vehicle is aligned with the start waypoint so
--- that it points to the right direction and the implements can start work exactly at the waypoint)
---
--- The caller can pass in an already created alignment course with an index. In that case, we'll use
--- that course, starting at alignmentStartIx for the turn, otherwise a new course is created from
--- the vehicle's current position to startIx in fieldWorkCourse.
---
---@param fieldWorkCourse Course fieldwork course
---@param startIx number index of waypoint of fieldWorkCourse where the work should start
---@param alignmentCourse Course an optional course if the caller already has one
---@param alignmentStartIx number index to start the alignment course (if supplied)
function AIDriveStrategyFieldWorkCourse:startAlignmentTurn(fieldWorkCourse, startIx, alignmentCourse, alignmentStartIx)
    if alignmentCourse then
        -- there is an alignment course, use that one, if there is a start ix, then only
        -- the part starting at startIx
        alignmentCourse = alignmentCourse:copy(self.vehicle, alignmentStartIx)
    else
        -- no alignment course given, generate one
        alignmentCourse = self:createAlignmentCourse(fieldWorkCourse, startIx)
    end
    self.ppc:setShortLookaheadDistance()
    if alignmentCourse then
        local fm, bm = self:getFrontAndBackMarkers()
        self.turnContext = RowStartOrFinishContext(self.vehicle, fieldWorkCourse, startIx, startIx, self.turnNodes, self:getWorkWidth(), fm, bm,
                self:getTurnEndSideOffset(), self:getTurnEndForwardOffset())
        self.aiTurn = StartRowOnly(self.vehicle, self, self.ppc, self.turnContext, alignmentCourse, fieldWorkCourse, self.workWidth)
        self.state = self.states.DRIVING_TO_WORK_START_WAYPOINT
    else
        self:debug('Could not create alignment course to first up/down row waypoint, continue without it')
        self.state = self.states.WAITING_FOR_LOWER
        self:lowerImplements()
    end
end

-- switch back to fieldwork after the turn ended.
---@param ix number waypoint to resume fieldwork after
---@param forceIx boolean if true, fieldwork will resume exactly at ix. If false, we'll look for the next waypoint
--- in front of us.
function AIDriveStrategyFieldWorkCourse:resumeFieldworkAfterTurn(ix, forceIx)
    self.ppc:setNormalLookaheadDistance()
    self.state = self.states.WORKING
    self:lowerImplements()
    -- restore our own listeners for waypoint changes
    self.ppc:registerListeners(self, 'onWaypointPassed', 'onWaypointChange')
    local startIx = forceIx and ix or self.course:getNextFwdWaypointIxFromVehiclePosition(ix,
            self.vehicle:getAIDirectionNode(), self.workWidth / 2)
    self:startCourse(self.course, startIx)
end

function AIDriveStrategyFieldWorkCourse:checkTransitionFromConnectingTrack(ix, course)
    if course:isOnConnectingTrack(ix) then
        -- passed a connecting track waypoint
        -- check transition from connecting track to the up/down rows
        -- we are close to the end of the connecting track, transition back to the up/down rows with
        -- an alignment course
        local d, firstUpDownWpIx = course:getDistanceToFirstUpDownRowWaypoint(ix)
        self:debug('up/down rows start in %d meters, at waypoint %d.', d or -1, firstUpDownWpIx or -1)
        -- (no alignment if there is a turn generated here)
        if d < 5 * self.turningRadius and firstUpDownWpIx and not course:isTurnEndAtIx(firstUpDownWpIx) then
            self:debug('End connecting track, start working on up/down rows (waypoint %d) with alignment course if needed.', firstUpDownWpIx)
            self:startAlignmentTurn(course, firstUpDownWpIx)
        end
    end
end

-----------------------------------------------------------------------------------------------------------------------
--- Static parameters (won't change while driving)
-----------------------------------------------------------------------------------------------------------------------
function AIDriveStrategyFieldWorkCourse:setAllStaticParameters()
    AIDriveStrategyCourse.setAllStaticParameters(self)
    self:setFrontAndBackMarkers()
    self.loweringDurationMs = AIUtil.findLoweringDurationMs(self.vehicle)
    self.fieldWorkerProximityController = FieldWorkerProximityController(self.vehicle, self.workWidth)
end

-----------------------------------------------------------------------------------------------------------------------
--- Dynamic parameters (may change while driving)
-----------------------------------------------------------------------------------------------------------------------
function AIDriveStrategyFieldWorkCourse:getTurnEndSideOffset()
    return 0
end

function AIDriveStrategyFieldWorkCourse:getTurnEndForwardOffset()
    return 0
end

function AIDriveStrategyFieldWorkCourse:getImplementRaiseLate()
    return self.settings.raiseImplementLate:getValue()
end

function AIDriveStrategyFieldWorkCourse:getImplementLowerEarly()
    return self.settings.lowerImplementEarly:getValue()
end

function AIDriveStrategyFieldWorkCourse:rememberWaypointToContinueFieldWork()
    local ix = self:getBestWaypointToContinueFieldWork()
    self.vehicle:rememberCpLastWaypointIx(ix)
end

function AIDriveStrategyFieldWorkCourse:getBestWaypointToContinueFieldWork()
    local bestKnownCurrentWpIx = self.fieldWorkCourse:getLastPassedWaypointIx() or self.fieldWorkCourse:getCurrentWaypointIx()
    -- after we return from a refill/unload, continue a bit before the point where we left to
    -- make sure not leaving any unworked patches
    local bestWpIx = self.fieldWorkCourse:getPreviousWaypointIxWithinDistance(bestKnownCurrentWpIx, 10)
    if bestWpIx then
        -- anything other than a turn start wp will work fine
        if self.fieldWorkCourse:isTurnStartAtIx(bestWpIx) then
            bestWpIx = bestWpIx - 1
        end
    else
        bestWpIx = bestKnownCurrentWpIx
    end
    self:debug('Best return to fieldwork waypoint is %d', bestWpIx)
    return bestWpIx
end

function AIDriveStrategyFieldWorkCourse:setOffsetX()
    -- do nothing by default
end

function AIDriveStrategyFieldWorkCourse:isWorking()
    return self.state == self.states.WORKING or self.state == self.states.TURNING
end

--- Gets the current ridge marker state.
function AIDriveStrategyFieldWorkCourse:getRidgeMarkerState()
    return self.course:getRidgeMarkerState(self.ppc:getCurrentWaypointIx()) or 0
end

function AIDriveStrategyFieldWorkCourse:showAllInfo(note, ...)
    self:debug('%s: work width %.1f, turning radius %.1f, front marker %.1f, back marker %.1f',
            string.format(note, ...), self.workWidth, self.turningRadius, self.frontMarkerDistance, self.backMarkerDistance)
    self:debug(' - map: %s, field %s', g_currentMission.missionInfo.mapTitle,
            CpFieldUtil.getFieldNumUnderVehicle(self.vehicle))
    for _, implement in pairs(self.vehicle:getAttachedImplements()) do
        self:debug(' - %s', CpUtil.getName(implement.object))
    end
end


--- Updates the status variables.
---@param status CpStatus
function AIDriveStrategyFieldWorkCourse:updateCpStatus(status)
    ---@type Course
    if self.fieldWorkCourse then
        status:setWaypointData(self.fieldWorkCourse:getCurrentWaypointIx(), self.fieldWorkCourse:getNumberOfWaypoints())
    end
end

function AIDriveStrategyFieldWorkCourse:isTurnOnFieldActive()
    return self.settings.turnOnField:getValue()
end

-----------------------------------------------------------------------------------------------------------------------
--- Convoy management
----------------------------------------------------------------------------------------------------------------------
function AIDriveStrategyFieldWorkCourse:getProgress()
    return self.fieldWorkCourse:getProgress()
end

function AIDriveStrategyFieldWorkCourse:isDone()
    return self.fieldWorkCourse:getCurrentWaypointIx() == self.fieldWorkCourse:getNumberOfWaypoints()
end

function AIDriveStrategyFieldWorkCourse:getFieldWorkProximity(node)
    return self.fieldWorkerProximityController:getFieldWorkProximity(node)
end
-----------------------------------------------------------------------------------------------------------------------
--- Overwrite implement functions, to enable a different cp functionality compared to giants fieldworker.
--- TODO: might have to find a better solution for these kind of problems.
-----------------------------------------------------------------------------------------------------------------------
local function emptyFunction(object, superFunc,...)
    local rootVehicle = object.rootVehicle
    if rootVehicle.getJob then 
        if rootVehicle:getIsCpActive() then
            return
        end
    end
    return superFunc(object,...)
end
--- Makes sure the automatic work width isn't being reset.
VariableWorkWidth.onAIFieldWorkerStart = Utils.overwrittenFunction(VariableWorkWidth.onAIFieldWorkerStart, emptyFunction)
VariableWorkWidth.onAIImplementStart = Utils.overwrittenFunction(VariableWorkWidth.onAIImplementStart, emptyFunction)